lyx2.3 for Debian

[Wolfgang Engelmann]

I would like to install lyx2.3 under Debian GNU/Linux 8.7 (jessie). I 
use at the moment lyx-2.3.1beta-1. Where do I find the sources and what 
do I have to take care of (additional packages, installing etc)? The 
versions for debian in http://wiki.lyx.org/LyX/ are older onces:

stretch (stable): 2.2.2
buster/sid (testing/unstable): 2.2.3
Wolfgang